(in Axes / Projection)
Projection = sin (i.e. sphere, for orthographic projection), but car (plate carrée / cylindrical) is and Aitoff are also possible (will not rotate)
Uncheck Reflect longitude axis, (keep it checked only if coordinates are provided with W longitudes)
View Sky System: Equatorial,
(in Axis / Grid)
Increase Grid Crowding cursor value to 30 or 60° tick
For cylindrical maps:
(in Axes / Projection)
Projection = car (for 0° at center, range = 0-360°)
Projection = car0 (for 0° on left border)
• Standard setup for planetary maps in TOPCAT PlanePlot (cylindrical):
(in Axes / Range)
Set Max X value to 360
Central meridian will be on left sideleft border
• To put the central meridian at the center (range = -180 to 180):
(in Axes / Range)
Min / Max X = -180 / 180
(in Axes / Labels)
X Label = Longitude
• From v4.6-3, the SkyPlot window is more versatile for maps (see above)
Healpix generation from a table in TOPCAT
Healpix is a tesselation system on the sphere, which depends on a resolution/scale parameter. It provides regular sampling in surface, with no singularity (poles).
When using this system, TOPCAT will integrate elements included in the corresponding cells. The benefit is to easily get a combined map from sparse data; the result is also scalable in resolution: at least degradation is performed correctly by combining healpix cells.
Cell size (in FoV size, ie in longitude at Equator): scale 6 ~ 1°, 12 ~ 1', 18 ~ 1"
Map projections From the SkyPlot window, several map projections are available with this mode are (in Axes panel): "sin" (actually: orthographic, 3D), Aitoff (all surface visible, minimize deformations near the poles), and "car" (cylindrical).
• Open the SkyPlot panel, select table and Lon & Lat parameters in Position panelin Position panel, as well as Lon and Lat parameters (C1min and C2min for an EPN-TAP table)
• Go to Form panel, click on the big Forms button (green cross) and "Add SkyDensity" from the local menu. Uncheck the previous Mark Form
• Go back to Position panel, select Lon and Lat parameters (C1min and C2min for an EPN-TAP table)
• Back to • In the Form panel, select parameter to plot as Weight (will be weighted by density), select combine mode, and adjust scale. Healpix generation is performed on the fly, so all scales are OKcan be selected.
• Possibly adapt color scale in the Aux Axis tab (left menu)
• In the Form panel, you can either "Import" to create the integrated HEALPix table in TOPCAT at the current scale (2 columns: cell #, plotting parameter; only filled cells are present), or "Save" in a file in HEALPix-fits format (FITS formatting is more efficient than VOTable, as it is compressed).
• From v4• HEALPix-fits maps from TOPCAT (>v4.6-3, TOPCAT HEALPix-fits maps can ) open in Aladin and can be, e.g., superposed on a planetary HiPS. Aladin prototype v10.1 (based on v10.127) is required to plot the HEALPix map with correct orientation (set longitude = ascending in Properties panel of the HiPS).
This other method is adapted when you have only 1 or 0 data / healpix cell, ie if the grouping has already been done in a previous step (e.g., with an ADQL query to group data by healpix cellsHEALPix cells, or when opening a previous HEALPix-fits map). It is is not intended to group or average table rows in the cells interactively.
• Start If starting from a lon/lat table, first add a new synthetic column providing healpix cell number (right-click on table column header and enter new column description):
• When FoV have 4 corners (or only3only 3), use Add New Quadrilateral Plot in a SkyPlot or PlanePlot window
• Set the other graphical parameters as usual
If contours are more complex polygons, use the Polygon Form.
• If the table contains footprints provided through an STC-S Polygon string (in particular s_region in EPN-TAP tables):
This applies either to image contours, to individual FoV for spectra, or and to other situations:
Plotting on shape models in TOPCAT
If the table contains the Cartesian coordinates of individual measurements, TOPCAT can easily display this in 3D:
(the shape model is then actually included in the data - but only where measurements exist)